How many book did A have in your bookcase when she was 11 years old?

Question

A enjoy reading in her free time and keep every book A has ever read. When she was five, she read 2
books and every year after, she tripled the number of books she read. 

Answer 1

Well, let's do this numerically with a table:

 

  age     # of books read

------------------------------

     5                 2

     6                 6

     7                18

     8                54

     9              162

   10              486

-----------------------

 

  total            728